This invention relates to an elastic electric cable required for wiring in mechatronic apparatus such as articulated robots, transferable machines, and electronic apparatus.
Demand for the elastic cable has been raised since former days and, in response to this demand, spiral elastic cables composed of wires wound into a coil have been offered for use. With the recent development of mechatronic industry using robots, the abovesaid spiral cable have come into use as lead wires for transferable apparatus such as multi-joint arm apparatus, linearly reciprocating one, revolving one, twisting one, lifting one, and vibrating one or as an interface cable between electronic apparatus as computers. This kind of spiral elastic cable, however, has been followed by a drawback that the rate of elongation is low (only twice at the maximum) in proportion to a large outer diameter of the spiral of cable (about three times as much as the diameter of a straight cable). For increasing elasticity of the spiral cable, it is necessary to increase a diameter of the spiral or a length thereof. Accordingly, this type of spiral cable cannot be used for wiring in a narrow space such as the inner part of the robot arm and, when applied to wiring outside the apparatus, becomes obstructive because of a great length thereof. An increase in diameter of the spiral part and length of the cable leads to decrease in elasticity and prevents the use of the cable itself.
It is, therefore, an object of this invention is to provide an elastic electric cable which is capable of expanding and contracting while remaining straight, is small in diameter, and can be manufactured at low cost.
Another object of this invention is to provide an elastic electric cable which is in the shape of coiled spring (i.e., spiral) and further elastic even after stretched from spiral to approximate straight line in configuration.
Other objects, features, and advantages of this invention will become apparent from the accompanying drawings and the detailed description that will be made later.